1. Technical Field of the Invention
The present invention relates to compositions for floor polish. More specifically, it relates to compositions for floor polish which can form tough coatings exhibiting good gloss without polishing by, for example, a polishing machine when they are applied to surfaces of floors and dried. The thus-formed coatings are capable of being easily removed with a chemical means.
2. Related Art
Compositions for floor polish to be applied to floors made of wood, concrete, vinyl tiles, rubber tiles or the like should be capable of forming tough coatings of excellent gloss when they are applied to surfaces of floors and dried, while the formed coatings should be easily removed by a physical or chemical means. In particular, compositions for floor polish comprising water-borne resins yield excellent gloss without any polishing treatments by a polishing machine or the like when they are applied to floor materials and hence they are called compositions for floor polish of the non-buffable type. Various properties are required for such compositions for floor polish. For example, coatings formed from these compositions after drying should have gloss, should hardly stain with black heel marks and should have good durability. Further, in addition to these properties, they should be detergent resistant to such an extent that gloss is not lost by treatments with ordinary detergents. The coating should be easily removed with a chemical means, but not with a physical means, when coatings are unacceptably stained or damaged. Because the durability and the removability of the coatings are inconsistent with each other, attempts have been made to reconcile the two properties to form tough coatings showing good removability.
To this end, compositions for floor polish comprising emulsified copolymers incorporated with polyvalent metals have been proposed (Japanese Patent Un-examined Publication (KOKAI), hereinafter referred to as "JP-A", No. 47-14019). However, those compositions have the drawback that, when those compositions comprising polyvalent metal complexes are applied and dried, amines or ammonia contained in the complexes as ligands are vaporized upon decomposition of the complexes to generate an odor of amines or ammonia. Further, the polyvalent metal complexes used for these compositions for floor polish are heavy metal complexes such as those of zinc, cobalt, cadmium, nickel, chromium, zirconium, tin, tungsten and aluminum. These complexes are undesirable from the viewpoint of the prevention of environmental pollution.
Instead of the use of metal complexes, a method in which zinc oxide is dispersed in a polymer emulsion has also been proposed (JP-A-57-117552). This method comprises a step of dispersing zinc oxide in an emulsion containing an acrylic copolymer by, for example, agitation to obtain a stable composition for floor polish which does not generate amine odor when it is dried. However, zinc used in the composition is a heavy metal and hence the problem, i.e., unfavorableness to environmental sanitation, has not been solved. In addition, since zinc oxide is very difficult to be solubilized. Zinc oxide hardly enters into the polymer oil particles in the emulsion, and if the emulsion is left stand for a long period of time, the zinc oxide is disadvantageously precipitated.
In order to solve the problem concerning the precipitation of zinc oxide, compositions obtained by reacting transition metals such as zinc with polymers at a specific temperature have been also proposed (JP-A-2-219863). However, the metals used in these composition are heavy metals and hence the problem of environmental pollution still remained. In addition, it was also disclosed in this patent document that non-heavy metals such as divalent alkali earth metals are not suitable as a cross-linking agent.
Recently, it has been reported that calcium can be used as a metal cross-linking agent instead of heavy metals such as those mentioned above. For example, JP-A-4-325582, JP-A-5-5083, PCT International Publication W094/7959 and JP-A-5-263046 disclose processes for producing calcium cross-linked compositions for floor polish through reactions of polymer emulsions obtained by polymerization of ethylenically unsaturated monomers with calcium. Further, JP-A-6-25593 discloses a process for producing calcium cross-linked compositions for floor polish through polymerization of calcium salts of monomers. However, those compositions for floor polish utilize polymers obtained by polymerization of ethylenically unsaturated monomers (acrylic resins) as a main resin component and it leads to a problem that satisfactory wear resistance and durability of coatings formed from these composition cannot necessarily be obtained.
To improve durability and wear resistance of coatings, there have been proposed compositions for floor polish utilizing water-borne polyurethane resins as a main resin component. For example, Japanese Patent Publication (KOKOKU), hereinafter referred to as "JP-B", No. 64-11236, JP-B-62-205168 and JP-B-63-23972 disclose compositions for floor polish comprising polyvalent metal complexes. However, there have not been known any processes where water-borne polyurethane resins are directly reacted with polyvalent metals to obtain compositions for floor polish.
An object of the invention is to provide compositions for floor polish capable of forming tough coatings without utilizing heavy metals. More specifically, the object of the present invention is to provide compositions for floor polish capable of forming coatings showing excellent durability and wear resistance and being free of heavy metal pollution by utilizing calcium as a metal cross-linking agent.
Another object of the invention is to provide compositions for floor polish capable of forming coatings which can be easily removed by a chemical means.